function z = f(p)   
% 右端项f
z = -2 .* pi.^2 .* exp(pi .* (p(:,1) + p(:,2)))...
    .* ( sin(pi.* p(:,1)).* cos(pi.* p(:,2))...
    + cos(pi.* p(:,1)) .* sin(pi.* p(:,2)) );
end
